Metallic impurities present in a semiconductor thin film bring about degradation of withstand pressure of an oxide film and a crystal defect, to cause deterioration in semiconductor device characteristics. For this reason, in a device manufacturing process, analysis of impurities has been performed.
For example, when an object to be inspected is a native oxide film or an oxide film with a film thickness of smaller than 10 nm on a semiconductor substrate, the oxide film is decomposed by vapor phase decomposition using hydrofluoric acid, and a chemical solution is dropped onto the substrate having become hydrophobic, which is then scanned, to recover metallic impurities on the substrate into the chemical solution. Then, this chemical solution is directly analyzed by an Inductively Coupled Plasma Mass Spectrometry (hereinafter referred to as ICP-MS) spectrometer, or this chemical solution is dried on the substrate and analyzed by a Total-reflection X-Ray Fluorescence (hereinafter referred to as TXRF) spectrometer.
When the object to be inspected is an oxide film or a nitrogen-containing thin film with a thickness of 10 nm or more, a large amount of Si atoms remain in the chemical solution having recovered the metallic impurities by the foregoing method. The SI atoms remaining in this chemical solution make it difficult to perform metallic impurity analysis in a low concentration by use of the TXRF spectrometer. Further, in the case of performing analysis by use of the ICP-MS spectrometer after pretreatment of removing the SI atoms in the chemical solution, unintended mixture of contamination from a reagent, an environment or a container used in the pretreatment makes it difficult to perform metallic impurity analysis in a low concentration. Moreover, such pretreatment is performed by an operator and thus makes it difficult to perform rapid analysis at low cost, which has been problematical.